Internal combustion engines for vehicles, such as motor vehicles, are available in many different configurations, which may include different numbers and arrangements of cylinders, the cylinders having different ignition timings and/or ignition orders. Some engine configurations may lead to inherent imbalances in the forces exerted on the crank shaft of the engine during engine running. This can lead to reciprocating, rocking, or torsional vibrations of the crank shaft and/or engine.
Depending on the configuration of the engine, the vibrations may be first order, second order or higher order vibrations relative to the rotation of the engine crank shaft. Again, depending on the configuration of the engine, the severity of the vibrations may vary according to the running speed of the engine.
Many engines incorporate one or more balance shafts, comprising out-of-balance weights, which are driven by the engine to balance vibrations. It is often desirable to provide the out-of-balance weights such that they are separated by the greatest possible distance between them. Hence, it may be desirable for the balance shaft to extend substantially the entire length of the engine. However, the inventors herein have recognized that providing a balance shaft which extends through the engine introduces additional complexity to the construction of the engine, as such balance shafts may need to be adequately supported, lubricated, and driven synchronously with the engine. Additionally, the balance shaft itself many introduce packaging concerns for the engine.
According to an aspect of the present disclosure, there is provided a balance assembly for an engine. The balance assembly includes a first electric motor coupled to the engine and configured to rotate a first eccentric mass relative to the engine, the first eccentric mass being coupled to a first shaft of the first electric motor; and a second electric motor coupled to the engine and configured to rotate a second eccentric mass relative to the engine, the second eccentric mass being coupled to a second shaft of the second electric motor. The first and second electric motors are configured to rotate the first and second eccentric masses in order to balance a vibration characteristic of the engine and the first and second electric motors are provided on opposite longitudinal ends of the engine to each other.
In this way, two independent motors may be mounted onto the engine (e.g., on the cylinder block). Onto each motor is mounted an eccentric mass. The masses then rotate in concert with the engine crankshaft. This enables the deletion of expensive mechanical drives and disconnects the masses from the vehicle drive-train, which may have transferred error states. Further, by placing the motors and corresponding masses on opposite longitudinal ends of the engine, the masses may be located as far apart as possible, which increases system efficiency.
To avoid unnecessary duplication of effort and repetition of text in the specification, certain features are described in relation to only one or several aspects or embodiments of the invention. However, it is to be understood that, where it is technically possible, features described in relation to any aspect or embodiment of the invention may also be used with any other aspect or embodiment of the invention.